1. Field of Invention
The present invention relates to a display apparatus having a display device (which is also called an electro-optical device), an electronic appliance having a display apparatus, and a method of driving a display apparatus. More particularly, the invention relates to control technology of display grayscales (configuration of grayscale control).
2. Description of the Related Art
There is a display apparatus which uses an electro-optical device, in which luminance is changed according to an applied voltage or a flowing current, as a pixel display device. For example, a representative example of an electro-optical device in which luminance is changed according to an applied voltage is a liquid crystal display device, and a representative example of an electro-optical device in which luminance is changed according to a flowing current is an organic electro luminescence device (an organic electro luminescence (organic EL), an organic light emitting diode (OLED); hereinafter referred to as an “organic EL”). An organic EL display apparatus using the latter organic EL device is a so-called self-luminous display apparatus using an electro-optical device that is a self-luminous device as a pixel display device.
The display apparatus using the electro-optical device may adopt a simple (passive) matrix method or an active matrix method as its driving method. However, the display apparatus of the simple matrix method has the problems that it is difficult to realize a large-scaled high-definition display apparatus having a simple structure.
Because of this, an active matrix method which controls a pixel signal that is supplied to a light-emitting device within a pixel using an active device installed within the pixel, for example, an insulated gate type field effect transistor (generally, a thin film transistor (TFT)), as a switching transistor has been actively developed.
In the case where the electro-optical device performs display, a switching transistor (sampling transistor) receives an input image signal that is supplied through an image signal line in a maintenance capacitance (which is also called a pixel capacitance) installed in a gate (control input terminal) of a driving transistor, and supplies a driving signal according to the received input image signal to the electro-optical device.
In the liquid crystal display apparatus using a liquid crystal display device as an electro-optical device, the liquid crystal display device is a voltage drive type device, and thus is driven just by a voltage signal according to the input image signal that is received in the maintenance capacitance. By contrast, in a display apparatus using a current drive type device such as an organic EL device as an electro-optical device, a driving transistor converts a driving signal (voltage signal) according to the input image signal that is received in the maintenance capacitance into a current signal, and supplies the driving current to an organic EL device or the like.
Here, it is known that a threshold voltage or mobility of an active device (driving transistor) that drives an electro-optical device is varied by a process change or the environment. Accordingly, in order to uniformly control the display luminance throughout the entire screen of the display apparatus, configurations for correcting the luminance change due to the characteristic change of the above-described active device for driving in each pixel circuit (driving signal constant processing technique for constantly maintaining the driving signal) have been variously examined.